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Author Topic: Variable main jet, Wilsonia gauge and Paint code queries  (Read 168 times)
Wasim
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« on: June 19, 2022, 06:08:35 PM »
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Thanks in advance.

I have a twin carb set up for the grey motor with both carbs having a variable main jet (carbs have been rebuilt) - my query is - before fitting the carbs to the engine what is a good starting point with the variable jets - A quarter, half or full turn from closed??

With the Wilsonia gauge the amps read -30 to +30 amps (original generator puts out 29 amps) - if I fit a 55 amp alternator will the gauge still operator or is there something I have to do?

What is the correct name of this paint code 256 2058 - is it Duchess Green, Glade green or something else?

Regards, Wasim
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Thompson Beach, South Australia
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« Reply #1 on: June 19, 2022, 08:00:39 PM »
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Wasim,

Ammeter:  If your alternator charges at more than 30 amps, your ammeter will go off-scale.  That's all.

Variable main jets:  There's an old saying which says, "Lean the mixture out until the exhaust valves burn.  Enrich the mixture a quarter-turn, recondition the cylinder head, and then you're set."  Its main purpose is to illustrate what can go wrong with variable main jets.

Use fixed jets instead.  If your carburettors have 1-1/32" venturis (BXOV-1), 51 main jets are recommended.  If your carburettors have venturi restrictors fitted, you need to go down a couple of sizes.

Rob
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Harv
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« Reply #2 on: June 20, 2022, 07:12:31 AM »
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My thinking is similar to Robs... variable main jets are not a good thing.

Adjustable main jets have their good points (you only need to buy one adjustable jet rather than several fixed jets to get the right one), together with their shortcomings (the temptation to fiddle with them or go hunting for better fuel economy can lead to over-lean conditions and burnt valves, the o-ring seal can leak over time).

If you are still keen on keeping them, as an initial tuning point the following may be used:
• bring the engine up to operating temperature,
• hold the engine speed at around 3000-3500rpm (mid throttle).
• slacken the lock nut on the adjustable jet then screw the adjuster in slowly until the engine speed starts to alter and run a little bit rough. Wind back the adjuster until the engine speed pick up and the engine no longer runs rough.
• tighten the lock nut.

Whilst this is a valid process, the info below is probably just as valid. I found these numbers by flow testing a number of adjustable jets:
• Two turns open:    0.043"
• Three turns open:    0.061"
• Four turns open:   0.067"
• Wide, wide open:   0.073"

This would suggest that as a starting point for most grey motors that 2½ turns open is a good guess, whilst for twins and triples a shade over two turns open is a good starting point.

Once you have a starting point, it pays to be wary.
•   read the spark-plugs, or
•   measuring exhaust gas carbon monoxide/oxygen, and
Either of these methods should be undertaken in conjunction with road testing, looking for stumbles, flat spots, drivability and fuel consumption.

Cheers,
Harv
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mcl1959
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« Reply #3 on: June 20, 2022, 08:28:50 AM »
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256-2058 is not a Holden colour. It has been identified twice by me as a mistake printing on a plate which was supposed to be 256-2038 which is Duchess green.   All plates have two ways of identifying the external colours. One is in the trim line and the other is on the paint line.  If the two identifiers don’t line up then an error has occurred.

Glade green is 585-9693 and is an FB EK colour.
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Wasim
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« Reply #4 on: June 20, 2022, 05:34:02 PM »
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Thank you for all the replies - plenty to think about.

Regards, Wasim
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Thompson Beach, South Australia
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« Reply #5 on: June 20, 2022, 09:18:52 PM »
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Wasim

In Accesory of the week section there is a 50 amp version of the Wilsonia gauge

They do turn up occasionally

Gary
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my8thholden
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« Reply #6 on: June 21, 2022, 06:27:03 AM »
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Gents ..who do you go to for your choice of main jets ? ...thx Vern ..
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Harv
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« Reply #7 on: June 21, 2022, 07:21:31 AM »
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eBay for main jets.

Most are from Genuine Stromberg - Clive is still churning out the jets in a variety of sizes:
https://www.stromberg-97.com/product-index/parts/?cat=genuine-97-jets-and-valves

Cheers,
Harv

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